WO2014071630A1 - Safety electric-heating circuit, safety electric-heating method, and electric heater - Google Patents

Abstract

Provided are a safety electric-heating circuit, a safety electric-heating method, and an electric heater. The circuit comprises: a control unit (1), for outputting a heating control signal according to a user instruction and outputting a first safety indication signal during the normal operation; a first switch unit (2), being switched on or switched off according to the heating control signal, and outputting a second safety indication signal according to the first safety indication signal during the normal operation; a protection unit (3), for outputting a safety operating signal when the second safety indication signal is received, and outputting a warning signal when the second safety indication signal is not received; a second switch unit (4), being switched on when the safety operating signal is received and being switched off when the warning signal is received; and an electric-heating unit (5), for providing heat when the first switch unit (2) and the second switch unit (4) are switched on. The protection unit (3) performs safety monitoring on the control unit (1) and the first switch unit (2), thereby ensuring electric-heating safety and avoiding a fire disaster as the electric heater loses control due to a circuit failure during heating.

Description

 Safety electric heating circuit, safety electric heating method and electric heating heater Technical field

The invention belongs to the field of electric heating and heating, and particularly relates to a safe electric heating circuit, a safe electric heating method and an electric heating heater.

Background technique

At present, there are many types of electric heaters such as electric heating, electric heating and the like, and there are high-voltage alternating current electric heater products that use electric high-voltage alternating current to heat electric heating wire, and use a voltage conversion device to convert high-voltage alternating current into low-voltage direct current and then electric heating the electric heating wire. The low-voltage DC electric heater product has a high-voltage direct-current electric heater product that uses a voltage conversion device to convert high-voltage alternating current into high-voltage direct current and then heats the electric heating wire, and uses a voltage conversion device to convert the high-voltage alternating current into a low-voltage alternating current and then heat the electric heating wire. Low-voltage AC heater products, different electrothermal products have different electric heating circuits.

Generally, in an electric heater product using high-voltage alternating current, the electric heating wire can be electrically heated by the positive half cycle of the sine wave of the alternating current power source, and the negative half cycle of the sine wave of the alternating current power source is used for safety induction protection, which is relatively safe, but the current market On the other hand, for the electric heater products using direct current, most of the non-circuit safety protection measures are prone to cause the heating element to continue to heat up due to circuit failure, causing high temperature fire and poor safety performance.

technical problem

The purpose of the embodiments of the present invention is to provide a safe electric heating circuit, which aims to solve the problem that the electric heating circuit currently using direct current has poor safety performance, and the heating element is prone to temperature rise due to circuit failure, thereby causing high temperature fire.

Technical solution

The embodiment of the invention is implemented as follows, a safety electric heating circuit, the circuit comprising:

a control unit, configured to output a heating control signal according to a setting instruction of the user, and output a first safety indication signal during normal operation;

a first switch unit, configured to be turned on or off according to the heating control signal, and output a second safety indication signal according to the first safety indication signal during normal operation;

a protection unit, configured to output a safe working signal when receiving the second safety indication signal, and output an alarm signal when the second safety indication signal is not received;

a second switching unit, configured to be turned on when receiving the safe working signal, and turned off when receiving the alarm signal;

An electric heating unit, configured to perform heating when both the first switching unit and the second switching unit are turned on;

The connection relationship between the first switch unit, the second switch unit, and the electric heating unit is:

a positive working terminal of the second switching unit is connected to a current input end of the second switching unit, and a current output end of the second switching unit is connected to a current input end of the electric heating unit, and the current output end of the electric heating unit and the first a current input end of a switching unit is connected, and a current output end of the first switching unit is connected to a negative pole of the DC working power supply; or

The positive electrode of the DC power supply is connected to the current input end of the electric heating unit, the current output end of the electric heating unit is connected to the current input end of the second switch unit, and the current output end of the second switch unit is a current input end of the first switching unit is connected, and a current output end of the first switching unit is connected to a negative pole of the DC working power supply; or

The positive pole of the DC power supply is connected to the current input end of the electric heating unit, and the current output end of the electric heating unit is connected to the current input end of the first switch unit, and the current output end of the first switch unit The current input end of the second switching unit is connected, and the current output end of the second switching unit is connected to the negative pole of the DC working power supply;

The dual power supply end of the control unit is connected to both ends of the DC working power supply, the input end of the control unit receives a setting instruction of an external user, and the output end of the control unit is connected to the control end of the first switching unit. The dual power supply end of the protection unit is connected to both ends of the DC working power supply, and the input end of the protection unit is connected to the safety indication signal output end of the first switch unit, and the output end of the protection unit and the second switch The control terminal of the unit is connected.

Another object of embodiments of the present invention is to provide an electric heater that employs the above-described safety electric heating circuit.

Another object of embodiments of the present invention is to provide a method of safe electric heating, the method comprising the following steps:

The control unit outputs a heating control signal according to a setting instruction of the user, and outputs a first safety indication signal during normal operation;

The first switch unit is turned on or off according to the heating control signal, and outputs a second safety indication signal according to the first safety indication signal during normal operation;

The protection unit outputs a safety operation signal when receiving the second safety indication signal, and outputs an alarm signal when the second safety indication signal is not received;

The second switch unit is turned on when receiving the safe working signal, and is turned off when the alarm signal is received;

The electrothermal unit performs a heating operation when both the first switching unit and the second switching unit are turned on.

Beneficial effect

According to the embodiment of the present invention, the safety control of the control unit and the first switch unit is performed by the protection unit, and the electric heating safety is ensured without affecting the temperature control of the electric heating unit by the control unit, thereby avoiding the failure of the electric heating heater product due to the circuit. The heating is out of control, which is easy to cause a safety hazard of high temperature fires. At the same time, the safety electric heating circuit has a simple structure and low cost.

DRAWINGS

1(a) to 1(f) are structural diagrams of a safety electric heating circuit according to an embodiment of the present invention;

2 is a circuit diagram showing an example of a safety electric heating circuit according to an embodiment of the present invention;

3 is another example circuit diagram of a control unit in a safety electric heating circuit according to an embodiment of the present invention;

FIG. 4 is a flowchart showing an implementation of a safe electric heating method according to an embodiment of the present invention;

FIG. 5 is a flowchart of an implementation of step S101 in FIG. 4.

Embodiments of the invention

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

According to the embodiment of the present invention, the safety control of the control unit and the first switch unit is performed by the protection unit, and the electric heating safety is ensured without affecting the temperature control of the electric heating unit by the control unit, thereby solving the circuit failure of the electric heating heater product. Uncontrolled heating can easily cause high temperature fires.

FIG. 1 shows the structure of a safety electric heating circuit according to an embodiment of the present invention. For the convenience of description, only parts related to the present invention are shown.

As an embodiment of the invention, the safety electric heating circuit can be applied to various electric heating heaters, including:

The control unit 1 is configured to output a heating control signal according to a setting instruction of the user, and output a first safety indication signal during normal operation;

The first switch unit 2 is configured to be turned on or off according to the heating control signal, and output a second safety indication signal according to the first safety indication signal during normal operation;

The protection unit 3 is configured to output a safe working signal when receiving the second safety indication signal, and output an alarm signal when the second safety indication signal is not received periodically;

a second switching unit 4, configured to be turned on when receiving a safe working signal, and turned off when receiving an alarm signal;

The electric heating unit 5 is configured to perform heating operation when both the first switching unit 2 and the second switching unit 4 are turned on.

The first switch unit 2, the second switch unit 4, and the electric heating unit 5 are connected in series through the current input end and the current output end, and are connected to the positive and negative poles (or the AC working power source) of the DC working power supply as a closed loop, which is not limited. There are six specific connection relationships according to their serial order, see Figure 1(a) - Figure 1(f), respectively:

Referring to FIG. 1( a ), the positive pole of the DC working power supply (or one end of the AC working power supply) is connected to the current input end of the second switching unit 4 , and the current output end of the second switching unit 4 is connected to the current input end of the electric heating unit 5 , The current output end of the electric heating unit 5 is connected to the current input end of the first switching unit 2, and the current output end of the first switching unit 2 is connected to the negative pole of the DC working power supply (or the other end of the AC working power supply); or

Referring to FIG. 1(b), the positive pole of the DC working power supply (or one end of the AC working power supply) is connected to the current input end of the electric heating unit 5, and the current output end of the electric heating unit 5 is connected to the current input end of the second switching unit 4, and the second switch The current output end of the unit 4 is connected to the current input end of the first switch unit 2, and the current output end of the first switch unit 2 is connected to the negative pole of the DC working power supply (or the other end of the AC working power supply); or

Referring to FIG. 1(c), the positive pole of the DC working power supply (or one end of the AC working power supply) is connected to the current input end of the electric heating unit 5, and the current output end of the electric heating unit 5 is connected with the current input end of the first switching unit 2, first The current output end of the switch unit 2 is connected to the current input end of the second switch unit 4, and the current output end of the second switch unit 4 is connected to the negative pole of the DC working power supply (or the other end of the AC working power supply); or

Referring to FIG. 1(d), the positive pole of the DC working power supply (or one end of the AC working power supply) is connected to the current input end of the first switching unit 2, and the current output end of the first switching unit 2 is connected to the current input end of the electric heating unit 5, The current output end of the electrothermal unit 5 is connected to the current input end of the second switch unit 4, and the current output end of the second switch unit 4 is connected to the negative pole of the DC working power supply (or the other end of the AC working power supply); or

Referring to FIG. 1(e), the positive current of the DC working power supply (or one end of the AC working power supply) is connected to the current input end of the first switching unit 2, and the current output end of the first switching unit 2 and the current input end of the second switching unit 4 Connected, the current output end of the second switch unit 4 is connected to the current input end of the electric heating unit 5, and the current output end of the electric heating unit 5 is connected to the negative pole of the DC working power supply (or the other end of the AC working power supply); or

Referring to FIG. 1(f), the positive current of the DC working power supply (or one end of the AC working power supply) is connected to the current input end of the second switching unit 4, and the current output end of the second switching unit 4 and the current input end of the first switching unit 2 Connected, the current output end of the first switch unit 2 is connected to the current input end of the electric heating unit 5, and the current output end of the electric heating unit 5 is connected to the negative pole of the DC working power supply (or the other end of the AC working power supply);

In addition, the dual power supply end of the control unit 1 is connected to both ends of the power supply, and the input end of the control unit 1 receives the setting instruction of the external user, and the output end of the control unit 1 is connected to the control end of the first switching unit 2;

The dual power supply end of the protection unit 3 is connected to both ends of the power supply, the input end of the protection unit 3 is connected to the safety indication signal output end of the first switch unit 2, and the output end of the protection unit 3 is connected to the control end of the second switch unit 4. ;

In the embodiment of the present invention, the input end of the control unit 1 can perform parameter setting according to a setting instruction of the user, and the parameter setting can be set when the safety electric circuit is operated for the first time. There is no need to repeat the settings at startup, and you can reset them if you need to change the parameters.

In the embodiment of the present invention, the power source can adopt an alternating current working power source, but is particularly suitable for the electric heat protection of the direct current working power source.

The control unit 1 can be a temperature control unit, and detects the temperature of the electric heating unit 5 through the temperature detecting module, and outputs a temperature control signal according to the temperature of the electric heating unit 5 to control the on/off of the first switching unit 2, thereby implementing the electric heating unit 5. Control of heating work.

In the embodiment of the present invention, the control unit controls the on/off of the first switch unit by the heating control signal, thereby controlling the temperature control of the heating unit, and outputs a safety indication signal to the protection unit when the control unit and the first switch unit operate normally. The protection unit can perform safety monitoring on the control unit and the first switch unit, and control the second switch unit to cut off the heating unit when an abnormality occurs in the control unit or the first switch unit (ie, the safety indication signal cannot be received) in an unsafe working state. The power supply is prevented from causing the first switching tube unit to be turned on for a long time due to the control unit failure or the first switching unit device being damaged, thereby causing a high temperature accident caused by the heating unit being out of control due to heating.

In the embodiment of the invention, the control unit and the first switch unit are safely monitored by the protection unit, and the electric heating safety is ensured without affecting the temperature control of the electric heating unit by the control unit, thereby avoiding the heating of the electric heating heater product due to the circuit failure, resulting in heating Out of control, it is easy to cause safety hazards of high temperature fires, and the safety electric heating circuit has a simple structure and low cost.

FIG. 2 shows an exemplary circuit of a safety electric heating circuit according to an embodiment of the present invention, and for convenience of explanation, only parts related to the present invention are shown.

As an embodiment of the invention, the control unit 1 comprises:

Resistor R10, resistor R11, resistor R12, resistor R13, resistor R14, resistor R15, resistor R16, resistor R17, resistor R18, resistor R19, resistor R20, temperature setting module 11, temperature sensing module 12, capacitor C3, diode D3, diode D4, third operational amplifier U3, fourth operational amplifier U4;

One end of the resistor R10 is the positive power supply end of the control unit 1, the other end of the resistor R10 is connected to one end of the resistor R12, the other end of the resistor R12 is the negative power supply end (ground) of the control unit 1, and the common end of the resistor R10 and the resistor R12 Connected to the forward input terminal of the third operational amplifier U3 through the resistor R11, the forward input terminal of the third operational amplifier U3 is also connected to the output terminal of the third operational amplifier U3 through the resistor R14, and the reverse input of the third operational amplifier U3 The terminal is connected to one end of the resistor R15, one end of the resistor R13, and one end of the capacitor C3. The other end of the resistor R15 is connected to the output terminal of the third operational amplifier U3, and the other end of the resistor R13 is connected to the anode of the diode D3. The cathode is connected to the output terminal of the third operational amplifier U3, the other end of the capacitor C3 is also the negative power supply terminal (ground) of the control unit 1, the third operational amplifier U3 is also connected to the cathode of the diode D4, and the anode of the diode D4 and the resistor R16 One end of the resistor R16 is connected to the positive power supply terminal of the control unit 1 and connected to one end of the resistor R18, and the other end of the resistor R18 is electrically connected to the temperature detecting module 12. The input end is connected, the current output end of the temperature detecting module 12 is connected to the negative power supply end (ground) of the control unit 1 and one end of the resistor R17, and the other end of the resistor R17 is connected to the current output end of the temperature setting module 11, and the temperature setting module 11 The current input terminal is connected to the anode of the diode D4, the set terminal of the temperature setting module 11 is the user input terminal of the control unit 1, the anode of the diode D4 is also connected to the forward input terminal of the fourth operational amplifier U4, and the fourth operational amplifier U4 The positive input terminal is connected to the output terminal of the fourth operational amplifier U4 through the resistor R19, the inverting input terminal of the fourth operational amplifier U4 is connected to the current input terminal of the temperature detecting module 12, and the output terminal and the resistor of the fourth operational amplifier U4 are connected. One end of the R20 is connected, and the other end of the resistor R20 is the output end of the control unit 1.

The temperature setting module 11 is configured to receive a setting instruction of the user, and adjust the output adjustment of the heating control signal according to the setting of the user, which can be implemented by using an adjustable resistor VR1, and one end of the adjustable resistor VR1 is the temperature setting module 11 At the current input end, the other end of the adjustable resistor VR1 is the current output end of the temperature setting module 11, and the adjusting end of the adjustable resistor VR1 is the set end of the temperature setting module 11.

The temperature detecting module 12 is configured to detect the real-time temperature of the electric heating unit 5, and convert the real-time temperature signal of the electric heating unit 5 into a current signal and feed back to the control unit 1 as an output adjustment of the heating control signal, so that the temperature of the electric heating unit 5 is constant to the user. The setting value. The temperature detecting module 12 can be implemented by using a temperature sensor or a metal-type temperature sensing wire or a thermistor RT1 having a temperature sensing characteristic. One end of the metal-type temperature sensing wire or the thermistor RT1 is a current input end of the temperature detecting module 12, The other end of the metal type temperature sensing wire or thermistor RT1 is the current output terminal of the temperature detecting module 12.

For example, in the embodiment of the present invention, the first switching unit 2 can be implemented by using a discrete switching device (such as a relay), or a semiconductor switching device (such as a MOS tube). , triode, thyristor, etc.) and resistor connection, the specific structure is:

a fourth switch tube 21, a resistor R21 and a resistor R22;

The control end of the fourth switch tube 21 is the control end of the first switch unit 2, the input end of the fourth switch tube 21 is the current input end of the first switch unit 2, and the output end of the fourth switch tube 21 is the first switch. The current output end of the unit 2 is connected to the control end of the fourth switch tube 21 through a resistor R21. One end of the resistor R22 is a safety indication signal output end of the first switch unit 2, and the other end of the resistor R22 is input to the fourth switch tube 21. End connection.

In the embodiment of the present invention, the fourth switch transistor 21 is an N-type MOS transistor Q4 as an example. The drain of the N-type MOS transistor Q4 is the input end of the fourth switch transistor 21, and the source of the N-type MOS transistor Q4 is the fourth. The output end of the switch tube 21, the gate of the N-type MOS transistor Q4 is the control end of the fourth switch tube 21;

Of course, the fourth switch tube 21 can also be implemented by an NPN type transistor. The collector of the NPN type transistor is the input end of the fourth switch tube 21, and the emitter of the NPN type transistor is the output end of the fourth switch tube 21, NPN type. The base of the triode is extremely the control end of the fourth switching tube 21.

The protection unit 3 comprises:

Resistor R5, resistor R6, resistor R7, resistor R8, resistor R9, capacitor C2, diode D1, diode D2, third switch transistor 31 and second operational amplifier U2;

One end of the resistor R9 is the input end of the protection unit 3, the other end of the resistor R9 is connected to the control end of the third switch tube 31, and the control end of the third switch tube 31 is connected to the output end of the third switch tube 31 through the resistor R8. The input end of the third switch tube 31 is connected to the anode of the diode D2, the cathode of the diode D2 is connected to the positive power supply end of the protection unit 3 and the end of the resistor R6, the other end of the resistor R6 is connected to one end of the capacitor C2, and the other end of the capacitor C2 The negative power supply end (ground) of the protection unit 3 is connected to the output end of the third switch tube 31, and the anode of the diode D2 and the other end of the resistor R6 are connected to the reverse input end of the second operational amplifier U2. The positive input terminal of the amplifier U2 is simultaneously connected with one end of the resistor R5 and one end of the resistor R7, the other end of the resistor R5 is the positive power supply end of the protection unit 3, and the other end of the resistor R7 is the negative power supply end (ground) of the protection unit 3. The forward input terminal of the second operational amplifier U2 is also connected to the anode of the diode D1, and the cathode of the diode D1 is connected to the output terminal of the second operational amplifier U2.

As a preferred embodiment of the present invention, the third switch tube 31 can be implemented by using an NPN type transistor Q3 or an N type MOS tube. The collector of the NPN type transistor Q3 is the input end of the third switch tube 31, and the NPN type transistor Q3 is used. The output end of the third switch tube 31 is substantially the base of the third switch tube 31; the drain of the N-type MOS tube is the input end of the third switch tube 31, and the source of the N-type MOS tube The output end of the third switch transistor 31 is extremely large, and the gate of the N-type MOS transistor is the control terminal of the third switch transistor 31.

The second switching unit 4 can be implemented by using a relay K1 or a semiconductor switching tube (such as a MOS tube, a triode, a thyristor, etc.), the high potential end of the relay K1 is connected to the power supply voltage, and the low potential end of the relay K1 is the second switching unit. The control terminal of 4, the common terminal of the relay K1 is the current input terminal of the second switching unit 4, the normally open end of the relay K1 is suspended, and the normally closed end of the relay K1 is the current output terminal of the second switching unit 4. The current input end of the semiconductor switch tube is the current input end of the second switch unit 4, the current output end of the semiconductor switch tube is the current output end of the second switch unit 4, and the control end of the semiconductor switch tube is the second switch unit 4 Control terminal.

In the embodiment of the present invention, the second switch unit 4 is an example of a P-type MOS transistor. The connection structure is such that the source of the P-type MOS transistor is the current input end of the second switch unit 4, and the drain of the P-type MOS transistor is the second switch. At the current output of unit 4, the gate of the P-type MOS transistor is the control terminal of the second switching unit 4.

The electric heating unit 5 can be heated by a metal type heating wire H1 or a carbon fiber heating wire or a heating cloth or a heat conductive film or a graphite electric heating plate and an electric heating tube material, and the metal type electric heating wire or carbon fiber electric heating wire or electric heating cloth or thermal conductive film or graphite electric heating plate The two ends of the electric heating tube are respectively a current input end and a current output end of the electric heating unit 5.

As a preferred embodiment of the present invention, if the control unit 1 and the protection unit 3 have a high stability of the power supply voltage or the operating power source is an AC power source, the safety electric heating circuit may further include a voltage stabilizing unit 6 for stabilizing the power supply voltage. Or convert the power supply voltage (convert the DC working power supply voltage or the AC working power supply voltage to the DC power supply voltage and stabilize the power supply voltage), and output the regulated power supply VDD to provide regulated power for the control unit 1, the protection unit 3, and the required unit. Further improving the overall stability of the safety electric heating circuit, the input end of the voltage stabilizing unit 6 is connected to the power supply voltage, and the positive output end of the voltage stabilizing unit 6 is simultaneously connected with the positive power supply end of the control unit 1 and the protection unit 3, and the voltage stabilizing unit 6 The negative output terminal is simultaneously connected to the negative power supply terminal of the control unit 1 and the protection unit 3.

In the embodiment of the present invention, the high potential end of the relay K1 in the second switching unit 4 can also be connected to the positive output end of the voltage stabilizing unit 6, and the voltage stabilizing unit 6 can be connected to the DC working power supply or can work with the alternating current. Power connection, when connecting different power supplies, select different voltage regulator chips or power conversion chips (AC-DC, DC-DC).

The voltage stabilizing unit 6 includes:

Voltage regulator chip U1 and capacitor C1;

An input end (Vin) of the voltage stabilizing chip U1 is an input end of the voltage stabilizing unit 6, and an output end (Vout) of the voltage stabilizing chip U1 is a positive output end of the voltage stabilizing unit 6 and the capacitor One end of the capacitor C1 is connected, and the other end of the capacitor C1 is grounded at the same time as the negative output terminal of the voltage stabilizing unit 6 and the ground terminal (GND) of the voltage stabilizing chip.

Here, the voltage regulator chip U1 can also be replaced by a power conversion chip to provide different power supply voltage values for other units.

The safety electric heating circuit may further comprise an alarm unit 7. The input end of the alarm unit 7 is connected to the output end of the protection unit 3 for sending an alarm message to the user through sound or display when receiving an alarm signal, for example, through a speaker. The audible alarm information, or the alarm information is displayed by the indicator light, and the sound and the displayed alarm information can be simultaneously issued or a higher-end liquid crystal display or energy-saving display can be adopted according to the actual needs of the user.

The alarm unit 7 includes:

Resistor R4 and light emitting diode LED1;

One end of the resistor R4 is the input end of the alarm unit 7, the other end of the resistor R4 is connected to the cathode of the LED II, and the anode of the LED and the positive output of the DC working power supply positive or voltage regulator unit 6 connection.

In the embodiment of the present invention, the fourth operational amplifier U4 in the control unit 1 and its peripheral component resistor R16, resistor R17, resistor R18, resistor R19, resistor R20, adjustable resistor VR1, metal type temperature sensitive wire or thermistor RT1 constitutes a temperature control circuit, the adjustable resistor VR1 is used to set the temperature control parameter, the metal type temperature sensitive wire or the thermistor RT1 is used to sense the temperature of the electric heating unit 5, and the temperature control circuit controls the temperature according to the adjustable resistance VR1. The parameter and the temperature of the metal type temperature sensing wire or the thermistor RT1 sense the temperature of the electric heating unit 5 to output an output heating control signal, that is, when the metal type temperature sensing wire or the thermistor RT1 senses that the temperature of the electric heating unit 5 is lower than the user setting. When the temperature control parameter is output, the high-level heating control signal signal is output. When the metal-type temperature sensing wire or the thermistor RT1 senses that the temperature of the electric heating unit 5 is higher than the temperature setting parameter set by the user, the heating control of the low level is output. Signal; operational amplifier U3 and its peripheral component resistor R10, resistor R11, resistor R12, resistor R13, resistor R14, resistor R15, capacitor C3, diode D3, diode D4 constitute a safe working signal generator, which can be used every other time A low-level signal is sent from the anode of the diode D4. (The diode D4 anode low-level signal is generated by the power supply VDD being a high voltage, the negative terminal of the capacitor C3 being ground, and the capacitor C3 being the lower input terminal of the operational amplifier U3. The output level of the operational amplifier U3 is high, the capacitor C3 is charged through the resistor R15, and the inverting input terminal of the operational amplifier U3 is gradually increased. When the voltage of the inverting input terminal is higher than the voltage of the same input terminal, the output of the operational amplifier U3 is low. Level, so that the anode output of diode D4 is a low level signal higher than a diode threshold of operational amplifier U3. At this time, C3 discharges the inverting input terminal of U3 through R13 and D3 to make it low level, and the operational amplifier The output of U3 is once again high level, so that it repeatedly sends a low level signal from the anode of diode D4 at intervals. The low level signal is input to the temperature control circuit as the first safety indication signal, and the temperature control circuit is followed. The output heating control signals are output together.

When the control unit 1 outputs a high-level heating control signal, the N-type MOS transistor Q4 in the first switching unit 2 is turned on to heat the electric heating unit 5, and when the control unit 1 outputs a low-level heating control signal, The N-type MOS transistor Q4 is turned off, and the electric heating unit 5 stops heating; when the control unit 1 outputs the heating control signal, there is a low-level signal output of the first safety indication signal at intervals, and when the low-level signal is input to the N When the gate of the MOS transistor Q4 is used, the drain of the N-type MOS transistor Q4 outputs a high-level signal, and the safe operation signal is converted from a low-level signal to a high-level signal (second safety indicating signal) from the N-type MOS transistor. The drain output of Q4.

The NPN type transistor Q3 in the protection unit 3 is used to discharge the electrolytic capacitor C2. When the input end of the protection unit 3 has the second safety indication signal input, the NPN type transistor Q3 is turned on, and the capacitor C2 is discharged when the input of the protection unit 3 is input. When the second safety indication signal is not input, the NPN transistor Q3 is turned off, and the resistor R6 charges the electrolytic capacitor C2. When the input end of the protection unit 3 has no second safety indication signal input for a long time, the control unit 1 or the first switch is indicated. Unit 2 has failed and causes N-type MOS transistor Q4 to be in a long-time conduction state, so resistor R6 charges electrolytic capacitor C2 for a long time, when electrolytic capacitor C2 positive voltage is charged higher than the positive input terminal of second operational amplifier U2 At the time of voltage, the second operational amplifier U2 outputs an alarm signal of a low level, controls the second switching unit 4 to cut off the electrothermal voltage of the electric heating unit 5, prevents the temperature of the electric heating unit 5 from being out of control and causes a safety accident, and when the output of the second operational amplifier U2 is low When the level alarm signal is issued, the alarm unit 7 can display an alarm through the LED 1 of the light-emitting diode to display a circuit failure.

When the protection unit 3 outputs a high level signal, the relay K1 in the second switching unit 4 is turned on, and the electric heating voltage is supplied to the electric heating unit 5. When the protection unit 3 outputs a low level signal, the relay K1 is turned off, and the electric heating unit is turned off. 5 electric heating voltage.

The three-terminal voltage regulator chip U1 and the capacitor C1 in the voltage stabilizing unit 6 are regulated and filtered to output a predetermined operating voltage.

In the embodiment of the invention, the control unit and the first switch unit are safely monitored by the protection unit, and the electric heating safety is ensured without affecting the temperature control of the electric heating unit by the control unit, thereby avoiding the heating of the electric heating heater product due to the circuit failure, resulting in heating Out of control, it is easy to cause safety hazards of high temperature fires, and the safety electric heating circuit has a simple structure and low cost.

FIG. 3 shows another example circuit of the control unit in the safety electric heating circuit provided by the embodiment of the present invention. For the convenience of description, only parts related to the present invention are shown.

As an embodiment of the present invention, the control unit 1 can also adopt the following structure:

Temperature setting module 11, temperature detecting module 12, microprocessor U5, resistor R26, resistor R27, resistor R28, resistor R29, resistor R30;

The current input end of the temperature setting module 11 is simultaneously connected with one end of the resistor R26 and one end of the resistor R27, the other end of the resistor R26 is the positive power supply end of the control unit 1, and the current output end of the temperature setting module 11 is the negative of the control unit 1. At the power supply end, the other end of the resistor R27 is connected to the first control terminal (PIN7) of the microprocessor U5, and the second control terminal (PIN8) of the microprocessor U5 is connected to the current input terminal of the temperature detecting module 12 via the resistor R28. The current output end of the detecting module 12 is the negative power supply end (ground) of the control unit 1, and the power supply end (PIN12) of the microprocessor U5 is connected to the positive power supply end of the control unit 1 and one end of the resistor R29, and the other end of the resistor R29 is The current input end of the temperature detecting module 12 is connected, the signal output end (PIN10) of the microprocessor U5 is connected to one end of the resistor R30, the other end of the resistor R30 is the output end of the control unit 1, and the ground end of the microprocessor U5 (PIN9) ) Grounding.

As an embodiment of the present invention, the control unit 1 may further include a digital display for displaying a working status. The digital display may select a plurality of display devices, such as a liquid crystal digital display, or a digital tube DS1 according to cost requirements and user requirements. The plurality of display inputs (pin ag, pin dp, + power pin, - power pin) of the digital display DS1 are respectively connected to the plurality of data outputs (PIN1-6, PIN15-18) of the microprocessor U5. .

As an embodiment of the present invention, the microprocessor U5 can adopt a processing chip of the MK7A25P model, and cooperate with a plurality of buttons and a temperature detecting module to implement temperature control, and output a heating control signal and a first safety indicating signal.

The temperature setting module 11 may further include:

First button SW1, second button SW2, third button SW3, fourth button SW4, resistor R22, resistor R23, resistor R24, resistor R25;

One ends of the first button SW1, the second button SW2, the third button SW3, and the fourth button SW4 are simultaneously connected to the current output terminal of the temperature setting module 11, the first button SW1, the second button SW2, the third button SW3, and the fourth button The other end of the button SW4 is connected to one end of the resistor R22, the resistor R23, the resistor R24, and the resistor R25, and the other ends of the resistor R22, the resistor R23, the resistor R24, and the resistor R25 are simultaneously connected to the current input terminal of the temperature setting module 11, first The control terminals of the button SW1, the second button SW2, the third button SW3, and the fourth button SW4 are a plurality of setting ends of the temperature setting module 11.

In the embodiment of the present invention, the user turns on the first button SW1, the second button SW2, the third button SW3, the fourth button SW4, and the corresponding current limiting resistors (resistor R22, resistor R23, resistor R24, and resistor R25). The shutdown and setting of the temperature control parameter, the microprocessor U5 outputs a heating control signal according to the temperature control parameter input by the user.

As an embodiment of the present invention, the user can also implement settings such as timing shutdown through multiple buttons to meet various practical needs of the user.

Another object of embodiments of the present invention is to provide an electric heater that employs the above-described safety electric heating circuit.

FIG. 4 shows an implementation flow of the safe electric heating method provided by the embodiment of the present invention. For the convenience of description, only parts related to the present invention are shown.

As an embodiment of the invention, the safe electrothermal method comprises the following steps:

In step S101, the control unit outputs a heating control signal according to a setting instruction of the user, and outputs a first safety instruction signal during normal operation;

In step S102, the first switching unit is turned on or off according to the heating control signal, and outputs a second safety indication signal according to the first safety indication signal during normal operation;

In step S103, the protection unit outputs a safety operation signal when receiving the second safety indication signal, and outputs an alarm signal when the second safety instruction signal is not received;

In step S104, the second switching unit is turned on when receiving the safe working signal, and is turned off when receiving the alarm signal;

In step S105, the electric heating unit performs a heating operation when both the first switching unit and the second switching unit are turned on.

As an embodiment of the present invention, after step S103, the following steps may be further included:

When an alarm signal is received, an alarm message is sent to the user by sound or display.

It is worth noting that this step (issuing alarm information to the user by sound or display when an alarm signal is received) may also be performed after step S104 or step S105.

In the embodiment of the invention, the control unit and the first switch unit are safely monitored by the protection unit, and the electric heating safety is ensured without affecting the temperature control of the electric heating unit by the control unit, thereby avoiding the heating of the electric heating heater product due to the circuit failure, resulting in heating Out of control, it is easy to cause safety hazards of high temperature fires, and the safety electric heating circuit has a simple structure and low cost.

Fig. 5 shows the implementation flow of step S101 in Fig. 4. For the convenience of explanation, only the parts related to the present invention are shown.

As an embodiment of the present invention, in step S101 in FIG. 4, the step of the control unit outputting the heating control signal according to the setting instruction of the user and outputting the first safety indication signal during stable operation is specifically as follows:

In step S201, initializing the settings;

In the embodiment of the present invention, the heating is first turned off, and the microprocessor U5 initializes the port and the memory, loads the initial temperature control parameter and the safety detection timing parameter into the memory when the memory is initialized, and then enters the sleep state.

In step S202, it is determined whether to start;

If yes, step S203 is performed to determine whether the initial power-on operation is performed;

If no, return to step S202;

In the embodiment of the present invention, after initializing the memory, the microprocessor U5 is in a sleep state, and the microprocessor U5 determines whether to start by the first button SW1 (ON/OFF), when the first button SW1 (ON/OFF) is pressed. When it is turned on, the control unit enters the running state, and the microprocessor U5 determines at any time whether the first button SW1 (ON/OFF) is pressed again. If the conduction is pressed again, the microprocessor U5 enters the sleep again. The state, that is, the control unit temporarily stops running until the first button SW1 (ON/OFF) is pressed again.

In step S203, it is determined whether the initial power-on operation is performed;

In the embodiment of the present invention, after the start of the entry, the CPU determines whether the control unit is initially powered on, and the initial power-on is that after the external power supply is turned on, the control unit enters the running state for the first time.

If yes, step S204 is performed, and the initial setting is a default temperature control parameter and a safety detection timing parameter;

If no, step S205 is executed to call the last set temperature control parameter and safety detection timing parameter;

In the embodiment of the present invention, when the control unit enters the running state, the microprocessor U5 saves the temperature control parameter and the safety detection timing parameter set by the user to the memory for the last time. If the user does not set the parameter, the microprocessor U5 The initial setting is set as the user's last parameter setting. When initial power-on operation, the microprocessor U5 sets the initial temperature control parameter and the safety detection timing parameter loaded when the memory is initialized as the default setting parameter; if the power is not cut off When the microprocessor U5 enters the running state again from the sleep state, the microprocessor U5 will call the temperature control parameter and the safety detection timing parameter set by the user for the last time, for example, when the first button SW1 (ON/OFF) is pressed. (Conduction), the control circuit firstly adds the working voltage to start the work, and sets the temperature control parameter and the safety detection timing parameter initially set to the memory as the default setting. Otherwise, the last set temperature control parameter and safety detection timing parameter are called. .

In step S206, the temperature control parameter is adjusted according to the user's needs;

In the embodiment of the present invention, the user enters the temperature control parameter adjustment interface by pressing the fourth button SW4 (SET), and after entering the temperature control parameter adjustment interface, the user passes the second button SW2 (UP) and the third button SW3 (DOWN). Perform temperature control parameter adjustment.

In step S207, acquiring a temperature detection parameter;

In the embodiment of the present invention, the temperature detecting parameter is obtained by the temperature detecting module, and by combining the resistance value R18 with the metal type temperature sensing wire or the thermistor RT1, the metal type temperature sensing wire or the thermistor RT1 is combined with FIG. 2 . The change in the partial pressure value represents a change in temperature to detect the real-time temperature of the electric heating unit, and the current temperature value can be displayed by a digital display device such as a digital tube or an LED.

In step S208, it is determined whether the temperature detection parameter is smaller than the temperature control parameter;

If yes, step S210 is performed to output a heated heating control signal;

If not, proceed to step S209, output a heating control signal to stop heating, and return to step S206;

In the embodiment of the present invention, the heating is continued when the current temperature detecting parameter does not reach the temperature control parameter, otherwise the control stops heating.

In step S211, it is determined whether the time of the safety detection timing parameter is reached;

If yes, proceed to step S212, perform security detection, output a first safety indication signal during normal operation, and return to step S206;

If not, the process returns directly to step S206.

In the embodiment of the present invention, when the time of the safety detection timing parameter is reached, the safety detection is performed. After the safety detection is completed, the safety detection timing parameter is reloaded into the memory, and the safety detection timing is performed, and then the process returns to step S206.

The present invention can also perform the timing shutdown parameter setting by using the second button SW2 (UP), the third button SW3 (DOWN), and the fourth button SW4 (SET). The specific setting process should be understood by those skilled in the art, and details are not described herein again. This embodiment does not limit the specific setting process of the timing shutdown parameter setting.

In the embodiment of the invention, the control unit and the first switch unit are safely monitored by the protection unit, and the electric heating safety is ensured without affecting the temperature control of the electric heating unit by the control unit, thereby avoiding the heating of the electric heating heater product due to the circuit failure, resulting in heating Out of control, it is easy to cause safety hazards of high temperature fires, and the safety electric heating circuit has a simple structure and low cost.

The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalents, and improvements made within the spirit and scope of the present invention should be included in the scope of the present invention. Inside.

Claims (17)

A safety electric heating circuit, characterized in that the circuit comprises: a control unit, configured to output a heating control signal according to a setting instruction of the user, and output a first safety indication signal during normal operation; a first switch unit, configured to be turned on or off according to the heating control signal, and output a second safety indication signal according to the first safety indication signal during normal operation; a protection unit, configured to output a safe working signal when receiving the second safety indication signal, and output an alarm signal when the second safety indication signal is not received; a second switching unit, configured to be turned on when receiving the safe working signal, and turned off when receiving the alarm signal; An electric heating unit, configured to perform heating when both the first switching unit and the second switching unit are turned on; The connection relationship between the first switch unit, the second switch unit, and the electric heating unit is: a positive working terminal of the second switching unit is connected to a current input end of the second switching unit, and a current output end of the second switching unit is connected to a current input end of the electric heating unit, and the current output end of the electric heating unit and the first a current input end of a switching unit is connected, and a current output end of the first switching unit is connected to a negative pole of the DC working power supply; or The positive electrode of the DC power supply is connected to the current input end of the electric heating unit, the current output end of the electric heating unit is connected to the current input end of the second switch unit, and the current output end of the second switch unit is a current input end of the first switching unit is connected, and a current output end of the first switching unit is connected to a negative pole of the DC working power supply; or The positive pole of the DC power supply is connected to the current input end of the electric heating unit, and the current output end of the electric heating unit is connected to the current input end of the first switch unit, and the current output end of the first switch unit The current input end of the second switching unit is connected, and the current output end of the second switching unit is connected to the negative pole of the DC working power supply; The dual power supply end of the control unit is connected to both ends of the DC working power supply, the input end of the control unit receives a setting instruction of an external user, and the output end of the control unit is connected to the control end of the first switching unit. The dual power supply end of the protection unit is connected to both ends of the DC working power supply, and the input end of the protection unit is connected to the safety indication signal output end of the first switch unit, and the output end of the protection unit and the second switch The control terminal of the unit is connected. The circuit of claim 1 wherein said control unit comprises: Resistor R10, resistor R11, resistor R12, resistor R13, resistor R14, resistor R15, resistor R16, resistor R17, resistor R18, resistor R19, resistor R20, setting module, temperature detection module, capacitor C3, diode D3, diode D4, Three operational amplifiers, fourth operational amplifiers; One end of the resistor R10 is a positive power supply end of the control unit, the other end of the resistor R10 is connected to one end of the resistor R12, and the other end of the resistor R12 is a negative power supply end of the control unit. a common terminal of the resistor R10 and the resistor R12 is connected to a forward input terminal of the third operational amplifier through the resistor R11, and a forward input terminal of the third operational amplifier is further connected to the An output terminal of the third operational amplifier is connected, and an inverting input terminal of the third operational amplifier is simultaneously connected to one end of the resistor R15, one end of the resistor R13, and one end of the capacitor C3, and the resistor R15 is further One end is connected to the output end of the third operational amplifier, the other end of the resistor R13 is connected to the anode of the diode D3, and the cathode of the diode D3 is connected to the output end of the third operational amplifier, the capacitor The other end of C3 is simultaneously the negative power supply end of the control unit, the third operational amplifier is also connected to the cathode of the diode D4, and the anode of the diode D4 is connected to one end of the resistor R16. The other end of the resistor R16 is connected to a positive power supply end of the control unit and one end of the resistor R18, and the other end of the resistor R18 is connected to a current input end of the temperature detecting module, and the current of the temperature detecting module The output terminal is connected to the negative power supply end of the control unit and connected to one end of the resistor R17, and the other end of the resistor R17 is connected to the current output end of the setting module, and the current input end of the setting module and the diode are An anode connection of D4, a set end of the setting module is an input end of the control unit, an anode of the diode D4 is further connected to a forward input end of the fourth operational amplifier, and a positive of the fourth operational amplifier Connected to the output terminal of the fourth operational amplifier through the resistor R19, the inverting input terminal of the fourth operational amplifier is connected to the current input terminal of the temperature detecting module, and the fourth operational amplifier is The output end is connected to one end of the resistor R20, and the other end of the resistor R20 is an output end of the control unit. The circuit of claim 2, wherein the setting module is an adjustable resistor, one end of the adjustable resistor is a current input end of the setting module, and the other end of the adjustable resistor is the The current output end of the module is set, and the adjustment end of the adjustable resistor is a set end of the setting module. The circuit of claim 1 wherein said control unit comprises: Setting module, temperature detecting module, microprocessor, resistor R26, resistor R27, resistor R28, resistor R29, resistor R30; The current input end of the setting module is simultaneously connected to one end of the resistor R26 and one end of the resistor R27, and the other end of the resistor R26 is a positive power supply end of the control unit, and the current output end of the setting module a negative power supply end of the control unit, the other end of the resistor R27 is connected to the first control end of the microprocessor, and the second control end of the microprocessor passes the resistor R28 and the temperature detection a current input end of the module is connected, a current output end of the temperature detecting module is a negative power supply end of the control unit, and a power supply end of the microprocessor is a positive power supply end of the control unit and one end of the resistor R29 Connected, the other end of the resistor R29 is connected to the current input end of the temperature detecting module, the signal output end of the microprocessor is connected to one end of the resistor R30, and the other end of the resistor R30 is the control At the output of the unit, the ground of the microprocessor is grounded. The circuit of claim 4 wherein said control unit further comprises a digital display for operational status display, said plurality of display inputs of said digital display being respectively associated with said plurality of data outputs of said microprocessor End connection. The circuit of claim 4 wherein said setting module comprises: First button, second button, third button, fourth button, resistor R22, resistor R23, resistor R24, resistor R25; One ends of the first button, the second button, the third button, and the fourth button are simultaneously connected to a current output end of the setting module, the first button, the second button, and the The third button and the other end of the fourth button are respectively connected to one end of the resistor R22, the resistor R23, the resistor R24, and the resistor R25, the resistor R22, the resistor R23, the The other end of the resistor R24 and the resistor R25 are simultaneously connected to the current input end of the setting module, and the control ends of the first button, the second button, the third button, and the fourth button are Set multiple settings of the module. The circuit according to any one of claims 2 to 6, wherein the temperature detecting module is a metal type temperature sensing wire or a thermistor, and one end of the metal type temperature sensing wire or the thermistor is The current input end of the temperature detecting module, and the other end of the metal type temperature sensing wire or the thermistor is a current output end of the temperature detecting module. The circuit of claim 1 wherein said first switching unit comprises: a fourth switch tube, a resistor R21 and a resistor R22; The control end of the fourth switch tube is a control end of the first switch unit, the input end of the fourth switch tube is a current input end of the first switch unit, and an output end of the fourth switch tube a current output end of the first switch unit is connected to a control end of the fourth switch tube through the resistor R21, and one end of the resistor R22 is a safety indication signal output end of the first switch unit, The other end of the resistor R22 is connected to the input end of the fourth switching transistor. The circuit of claim 1 wherein said protection unit comprises: Resistor R5, resistor R6, resistor R7, resistor R8, resistor R9, capacitor C2, diode D1, diode D2, third switch transistor, and second operational amplifier; One end of the resistor R9 is an input end of the protection unit, the other end of the resistor R9 is connected to a control end of the third switch tube, and the control end of the third switch tube passes the resistor R8 and the The output end of the third switch tube is connected, the input end of the third switch tube is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the positive power supply end of the protection unit and one end of the resistor R6. The other end of the resistor R6 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is a negative power supply end of the protection unit and an output end of the third switch tube, and an anode of the diode D2 The other end of the resistor R6 is connected to the inverting input terminal of the second operational amplifier, and the forward input terminal of the second operational amplifier is simultaneously connected to one end of the resistor R5 and one end of the resistor R7. The other end of the resistor R5 is the positive power supply end of the protection unit, the other end of the resistor R7 is the negative power supply end of the protection unit, and the forward input end of the second operational amplifier is further Anode connection of diode D1 The cathode of diode D1 is connected to the output terminal of the second operational amplifier to the output terminal of the protection unit. The circuit of claim 1 wherein said second switching unit is a relay or a semiconductor switching transistor; a high potential end of the relay is connected to a power supply voltage, a low potential end of the relay is a control end of the second switching unit, and a common end of the relay is a current input end of the second switching unit, the relay The normally open end is suspended, and the normally closed end of the relay is a current output end of the second switching unit; a current input end of the semiconductor switch tube is a current input end of the second switch unit, a current output end of the semiconductor switch tube is a current output end of the second switch unit, and a control end of the semiconductor switch tube It is the control end of the second switching unit. The circuit according to claim 1, wherein said electrothermal unit is a metal type electric heating wire or a carbon fiber electric heating wire or a electric heating cloth or a heat conductive film or a graphite electric heating plate or an electric heating tube. The circuit of claim 1 wherein said circuit further comprises: a voltage stabilizing unit, wherein an input end of the voltage stabilizing unit is connected to a positive pole of the DC working power supply, and a positive output end of the voltage stabilizing unit is simultaneously connected to a positive power supply end of the control unit and the protection unit, the stable The negative output end of the voltage unit is simultaneously connected to the control unit and the negative power supply end of the protection unit for stabilizing the DC working power supply voltage or converting the DC working power supply voltage, and outputting a regulated power supply. The circuit of any of claims 1 to 6, 8 to 12, wherein the circuit further comprises: An alarm unit, the input end of the alarm unit is connected to the output end of the protection unit, and is configured to send an alarm message to the user by sound or display when the alarm signal is received. An electric heating heater, characterized in that the electric heating heater comprises the circuit according to any one of claims 1 to 13. A safe electrothermal method, characterized in that the method comprises the following steps: The control unit outputs a heating control signal according to a setting instruction of the user, and outputs a first safety indication signal during normal operation; The first switch unit is turned on or off according to the heating control signal, and outputs a second safety indication signal according to the first safety indication signal during normal operation; The protection unit outputs a safety operation signal when receiving the second safety indication signal, and outputs an alarm signal when the second safety indication signal is not received; The second switch unit is turned on when receiving the safe working signal, and is turned off when the alarm signal is received; The electrothermal unit performs a heating operation when both the first switching unit and the second switching unit are turned on. The method according to claim 15, wherein said protection unit outputs a safe working signal when receiving said second safety indicating signal, and outputs an alarm signal when said second safety indicating signal is not received The following steps can also be included: When the alarm signal is received, an alarm message is sent to the user by sound or display. The method according to claim 15, wherein the step of outputting the heating control signal by the control unit according to the setting instruction of the user and outputting the first safety indicating signal during normal operation is specifically: S201, initial setting; S202, determining whether to start; If yes, execute S203; If no, return to execution S202; S203, determining whether the initial power-on work; If yes, execute S204; If no, execute S205; S204, the initial setting is a default temperature control parameter and a safety detection timing parameter; S205, calling the last set temperature control parameter and the safety detection timing parameter; S206, adjusting temperature control parameters according to user requirements; S207. Acquire temperature detection parameters. S208. Determine whether the temperature detection parameter is smaller than the temperature control parameter. If yes, execute S210; If no, execute S209; S209, output heating control signal to stop heating, and return to execution S206; S210, outputting a heating heating control signal; S211. Determine whether the time of the safety detection timing parameter is reached. If yes, execute S212; If no, return to execution S206; S212: Perform safety detection, output a first safety indication signal during normal operation, and return to S206.

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